A pretty awesome little project to come out of Mozilla research - a tool that allows you to record a program's execution and then replay back deterministically. It's like a core dump, but you can step through the program state (or even restart the program to "step backwards"). Can certainly think of several cases where a deterministic debugger would have been a real time saver.

This is awesome. The one downside that stands out for me is that it's not supported on 64 bit machines. I hope they fix that soon.

I agree. I remember being told in second year that we couldn't have debuggers that step backwards because it would be far too slow to step instruction at a time. But if you profile all the decisions made during execution, then you get deterministic execution. And then restarting is just as good as stepping backwards.

Yeah I know. It's such a simple but sensible way to deal with the reproducibility/stepping backwards issue. I wish I had thought of it.